The effect of kappa carrageenan and salt on thermoreversible gelation of methylcellulose
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Methylcellulose (MC) and kappa carrageenan (KCG) are widely used in food and pharmaceutical industries as a viscosity modifier, a gelling aid, and a film former due to their reversible thermal gelation properties. Thermoreversible gelation of MC/salt, MC/KCG/water, and MC/KCG/salt mixtures was investigated utilizing dynamic and steady shear rheological measurements. It was found that for the MC/salt mixture, gelation temperatures decreased linearly with increasing salt concentrations independent of valences of cations and molar concentrations of anions. For the MC/KCG blend, double gelation was not observed, and KCG is not influenced or disturbed the gelation properties of MC. Double gelation was observed for the mixture of MC/KCG/KCl for the low concentration of salts of 0.01 M KCl and 0.04 M KCl with the maximum moduli values for the mixture of MC/KCG/0.04 M KCl and then gradually decreased with increasing KCl salt concentration and eventually became similar to the gelation of MC solution. Therefore, KCl concentration played a major role in double gelation properties of MC/KCG/KCl mixture. It was also found that for the MC/KCG/KCl system, gelation transition matrices are linearly depending on salt concentration and independent of KCG and salt type. It was shown that for MC/salt mixture, solution rheology follows the principle of time–temperature superposition (TTS) below the gelation temperature. However, TTS failed above the gelation temperature. TTS also failed for MC/KCG and MC/KCG with low KCl concentration mixtures.
Authors are grateful to Dow Pharma and Food Solutions for providing the methylcellulose materials. We also acknowledge the financial support given by The Science of Advanced Materials at Central Michigan University.
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